Abnormality detecting method for automatic ice making machine

ABSTRACT

Disclosed is an abnormality detecting method for an automatic ice making machine that can quickly detect an abnormality to delay an ice-making time or an abnormality to shorten the ice-making time, if occurred. A down flow type ice making machine includes two ice making units, one control means, and an ice storage room. Each ice making unit has an ice making part, an ice-making water tank that stores ice-making water, a circulation pump that feeds the ice-making water stored in the ice-making water tank to the ice making part, and a float switch that detects the amount of the ice-making water in the ice-making water tank. Upon elapse of a preset first abnormality occurring time from a time of first detection of an ice-making complete water level by the float switch in any one of the ice making units, when the float switch in any one of the other ice making units has not detected the ice-making complete water level, the control means decides that an abnormality has occurred in the ice making unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an abnormality detecting method for an automatic ice making machine, and, more particularly, to an abnormality detecting method for an automatic ice making machine having a plurality of ice making units each of which circulates ice-making water stored in an ice-making water tank to an ice making part to produce ice blocks.

2. Description of the Related Art

A down flow type automatic ice making machine (hereinafter “down flow type ice making machine”) that causes ice-making water to flow to an ice making part to produce ice blocks is known as an automatic ice making machine that is placed in a kitchen or the like in a restaurant to continuously produce ice. Such down flow type ice making machines include one having a plurality of ice making units with an ice making part and an ice-making water tank, as disclosed in Japanese Patent Application Laid-Open No. 2004-69181. FIG. 4 is a schematic diagram showing the general configuration of a conventional down flow type ice making machine 12 having two ice making units 10, 10. An ice making part 14 in each ice making unit 10 is configured to have plural pairs of ice making plates 16, 16 in parallel, each pair of ice making plates 16, 16 being disposed opposite to each other, and an evaporation tube 18 extending from a freezing system (not shown) and disposed between the ice making plates 16, 16 in a meandering fashion.

Provided under each ice making unit 10 is an ice guide plate 20 tilting downward toward another ice making unit 10. The ice guide plate 20 has a plurality of return holes 22 formed therein to collect ice-making water which has been fed to the ice making part 14 but has not become frozen (unfrozen water) into an underlying ice-making water tank 24 via the return holes 22. The ice-making water tank 24 lying under the ice guide plate 20 is configured to be able to store a predetermined amount of ice-making water in the ice-making water tank 24. A float switch 26 is provided inside the ice-making water tank 24 to be able to detect the amount of the ice-making water in the ice-making water tank 24.

An ice-making water supply pipe 28 is connected to the ice-making water tank 24 to feed the ice-making water to the ice making part 14 via the supply pipe 28. The ice-making water supply pipe 28 is provided with a circulation pump 30 which pumps out the ice-making water in the ice-making water tank 24 to the ice making part 14. The ice-making water supply pipe 28 is connected to an ice-making water spray pipe 32 extending above the ice making part 14. An ice storage room 34 open upward is provided under the ice-making water tanks 24 of both ice making units 10, 10, so that ice blocks produced by the ice making units 10, 10 are discharged into the ice storage room 34. Two ice storage detection means 36, which are triggered when the ice storage room 34 becomes full of ice blocks, are provided in the ice storage room 34. That is, as shown in FIG. 4, each ice storage detection means 36 is provided in the ice storage room 34 in such a way as to be positioned at the crest portion of a mountain-like bulk (see reference numeral “B” in FIG. 4) formed by deposition of the ice blocks produced by each ice making unit 10, so that control means 38 provided at the down flow type ice making machine 12 stops the ice making operation when the ice storage detection means 36 detects ice blocks.

At the time of the ice making operation, the ice-making water is sprayed onto the ice-making surface of each ice making plate 16 via the ice-making water spray pipe 32 by the circulation pump 30, and a refrigerant is supplied to the evaporation tube 18 from the freezing system. The ice-making water, when flowing down on the ice-making surface cooled by the refrigerant, gradually starts being frozen on the ice-making surface, thereby producing ice blocks on the ice-making surface. Meanwhile, as ice blocks grow, the ice-making water in the ice-making water tank 24 is reduced, so that the float of the float switch 26 moves downward. When the ice blocks becomes a predetermined size in one ice making unit 10 and ice making is completed, the ice-making water in the ice-making water tank 24 reaches an ice-making complete water level (see FIG. 4). Then, the float switch 26 detects the event, and sends a detection signal to the control means 38. When the float switch 26 in the other ice making unit 10 detects the ice-making complete water level too, the control means 38 decides that ice making is completed, terminating the ice making operation. That is, the control means 38 decides that ice making is completed when every float switch 26, 26 detects the ice-making complete water level.

When the ice making operation is terminated, the control means 38 moves to a deicing operation, and feeds a hot gas to the evaporation tube 18 and feeds deicing water of normal temperature to the back side of the ice making plate 16 from a deicing water spray pipe (not shown). As a result, the ice making part 14 is heated by the hot gas and the deicing water, causing the ice blocks formed on the ice-making surface to be melted and fall down therefrom. The ice blocks dropped from the ice making part 14 are received and guided by the ice guide plate 20 to be discharged into the ice storage room 34.

Over years of usage, a stain formed by deposition of a scale, an impurity or the like on the ice-making surface or the like of the ice making plate 16 may be adhered thereto. If a stain is adhered to one of the ice making plates 16 in one of the ice making units, for example, the stain reduces the heat exchange efficiency, making it difficult to form ice blocks on that ice making plate 16. Then, the ice-making water to be frozen by the ice making plate 16 where an abnormality has occurred will be frozen by another ice making plate 16, so that ice blocks larger than the normal size are produced on a normal ice making plate 16. In this case, as the ice blocks become larger, the distance of the ice blocks from the ice-making surface becomes longer to reduce the heat exchange efficiency, making the time need to grow the ice blocks longer. In the ice making unit 10 where the abnormality has occurred, therefore, the ice-making water in the ice-making water tank 24 decreases gradually, so that the timing at which the float switch 26 detects the ice-making complete water level is delayed as compared with the normal case. In the normal ice making unit 10, on the other hand, the ice making operation progresses normally, so that the time needed for completion of the ice making operation is not delayed.

When large ice blocks are formed as mentioned above, upper and lower ice blocks may be connected together, or may ride over the partition separating the ice-making surface to be connected to the right-hand and left-hand side ice blocks. Such jointed ice blocks (hereinafter called “connected ice”) are hard to be deiced in the deicing operation, so that the deicing operation may be terminated with the connected ice remaining on the ice making plate 16. Then, the connected ice is subjected to ice making again in the ice making operation, resulting in double ice making. In this case, large connected ice is subjected to ice making, which significantly delays the ice making time due to the aforementioned reason. In consideration of the delay of the ice making time caused by an abnormality, therefore, the control means 38 in the conventional down flow type ice making machine 12 decides that an abnormality has occurred and terminates the ice making operation, when the time needed for every float switch 26, 26 to detect the ice-making complete water level exceeds a preset time (hereinafter called “abnormal delay time”).

SUMMARY OF THE INVENTION

However, the conventional abnormality detecting method needs to set the abnormal delay time as large as possible in order to prevent a slight delay of the ice making time from being erroneously detected as an abnormality. When an abnormality is detected by the conventional method, therefore, large ice blocks or connected ice may often be produced at the ice making part 14 already, so that the recovery takes time, resulting in an increase in the maintenance cost. In addition, ice blocks may deform or damage the ice making plate 16 or the like. That is, the conventional method has a shortcoming that an abnormality cannot be detected until production of abnormal ice blocks progresses considerably.

In a case where large ice blocks or connected ice are produced by the aforementioned occurrence of an abnormality, even if those ice blocks can be deiced by the deicing operation, the ice blocks may be caught by the ice guide plate 20. Then, in the ice making unit 10 where the abnormality has occurred, part of unfrozen water to be collected into the ice-making water tank 24 from the ice making part 14 flows down through the ice blocks on the ice guide plate 20 and falls down into the ice storage room 34 or the like, and may be collected into the ice-making water tank 24. As a result, the ice-making water in the ice-making water tank 24 decreases sooner, so that the ice making unit 10 where the abnormality has occurred detects the ice-making complete water level in a short period of time. According to the conventional abnormality detecting method, however, even when the ice making time is shortened this way, the control means 38 does not make an abnormality decision unless the ice making time exceeds the abnormal delay time, and keeps performing the operation. In other words, the conventional abnormality detecting method has a drawback that an abnormality which shortens the ice making time cannot be detected.

Accordingly, the invention addresses the foregoing inherent problems of the related art, and it is an object of the invention to provide an abnormality detecting method for an automatic ice making machine that can detect an abnormality which delays or shortens the ice making time at an early stage.

To overcome the problems and achieve the object, according to the invention, there is provided an abnormality detecting method for an automatic ice making machine comprising a plurality of ice making units each having an ice making part to be cooled by a refrigerant supplied from a freezing system, an ice-making water tank that stores ice-making water, a circulation pump that feeds the ice-making water stored in the ice-making water tank to the ice making part, and detection means provided at the ice-making water tank to detect an amount of the ice-making water in the ice-making water tank, and configured to collect unfrozen water which has been fed to the ice making part but has not been frozen into the ice-making water tank, and control means deciding that ice making is completed when every detection means detects that the ice-making water in the ice-making water tank has reached an ice-making complete water level at a time of an ice making operation,

wherein upon elapse of a preset first abnormality occurring time from a time of first detection of the ice-making complete water level by the detection means in any one of the ice making units, when the detection means in any one of the other ice making units has not detected the ice-making complete water level, the control means decides that an abnormality has occurred.

The abnormality detecting method for an automatic ice making machine according to the invention can quickly detect an abnormality which delays or shortens the ice making time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the general configuration of a down flow type ice making machine according to an embodiment;

FIG. 2 is a flowchart illustrating an operation method for the down flow type ice making machine;

FIG. 3 is a flowchart illustrating an operation method for a down flow type ice making machine according to a modification; and

FIG. 4 is a schematic diagram showing the general configuration of a down flow type ice making machine according to the related art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An abnormality detecting method for an automatic ice making machine according to the present invention will be described below by way of a preferred embodiment referring to the accompanying drawings. To avoid repeating the detailed description, same reference numerals are given to those components which are the same as the corresponding components of the above-described down flow type ice making machine according to the related art.

FIG. 1 is an explanatory diagram showing the schematic configuration of a down flow type ice making machine 40 which executes the abnormality detecting method according to an embodiment. The down flow type ice making machine 40 has a pair of ice making units 41, 41. An ice making part 14 in each ice making unit 41 is configured to have plural pairs of ice making plates 16, 16, each pair of ice making plates 16, 16 being disposed opposite to each other, and an evaporation tube 18 extending from a freezing system (not shown) and disposed between the ice making plates 16, 16 in a meandering fashion. An expansion valve 42 is intervened in each evaporation tube 18 on the inlet side of the ice making part 14, so that a refrigerant expanded and vaporized through the expansion valve 42 cools down the ice making part 14.

Provided under each ice making unit 41 at a position below the ice making part 14 is an ice guide plate 20 tilting downward toward another ice making unit 41. The ice guide plate 20 has a plurality of return holes 22 formed therein to collect unfrozen water into an ice-making water tank 24 via the return holes 22. A float switch (detection means) 26 is provided inside the ice-making water tank 24 to be able to detect the amount of the ice-making water.

An ice-making water supply pipe 28 is connected to the ice-making water tank 24 to feed the ice-making water to the ice making part 14 via the supply pipe 28. The ice-making water supply pipe 28 is provided with a circulation pump 30 which pumps out the ice-making water in the ice-making water tank 24. The ice-making water supply pipe 28 is connected to an ice-making water spray pipe 32 extending above the ice making part 14 to feed and spray the ice-making water onto the ice-making surface of each ice making plate 16 via the ice-making water spray pipe 32.

The ice-making water tank 24 is provided with a discharge pipe 44 which discharges excessive ice-making water (excessive water) remaining in the ice-making water tank 24 upon completion of the ice making operation. A discharge valve 46 which is normally urged in the direction of closing the discharge pipe 44 by urging means, such as a spring (not shown), is intervened in the discharge pipe 44. That is, at a normal time, the discharge valve 46 is not naturally released by the pressure of the ice-making water in the ice-making water tank 24, so that the ice-making water is not discharged. When the circulation pump 30 rotates reversely (in the direction opposite to the direction at the time of feeding the ice-making water), the water pressure releases the discharge valve 46 against the urging force of the urging means, allowing the excessive water to be discharged outside.

An ice storage room 34 open upward is provided under the ice-making water tanks 24, 24 of both ice making units 41, 41 to store ice blocks produced by the ice making parts 14, 14 of both ice making units 41, 41. One ice storage detection means 36, which is triggered when the ice storage room 34 becomes full of ice blocks, is provided in the ice storage room 34 in such a way as to be positioned substantially the center of both ice making units 41, 41 (on a middle line between the ice guide plates 20). That is, as the ice storage detection means 36 is provided at substantially the center position of both ice making units 41, 41, the ice storage detection means 36 detects an overlapping portion of the skirt portions of heaps of ice blocks deposited in the ice storage room 34 (see reference numeral “A” in FIG. 1).

The down flow type ice making machine 40 has control means 48 which performs the general operation control and determines an abnormality in the operation based on a detection signal from each float switch 26. The control means 48 incorporates two timers (first timer 50 and second timer 52) which will be described later, and controls the actuation of both timers 50, 52. The control means 48 is electrically connected to each float switch 26 to receive a detection signal therefrom when the float switch 26 detects the ice-making complete water level. The control means 48 is so set as to make a decision on the completion of the ice making operation when receiving the detection signal from every float switch 26, 26.

The control means 48 is also set so as to decide that an abnormality has occurred in any ice making unit 41 upon elapse of a preset first abnormality occurring time after reception of the detection signal from the float switch 26 which has detected the ice-making complete water level first, when the control means 48 has not received the detection signal (last detection of the ice-making complete water level) from the float switch 26 in the other ice making unit 41 (any one of the other ice making units 41). That is, the control means 48 makes an abnormality decision based on the difference between the ice making times of both ice making units 41, 41 (hereinafter called “ice making time difference”). This ice making time difference is measured by the first timer 50. Specifically, the first timer 50 starts operating to measure the ice making time difference when the control means 48 first receives the detection signal from any float switch 26. Accordingly, when an abnormality occurs in one ice making unit 41 to increase the ice making time difference, the control means 48 makes an abnormality decision to be able to detect the abnormality. Further, the control means 48 evenly makes a decision on an abnormality when the time measured by the first timer 50 passes the first abnormality occurring time, so that even when an abnormality which disables detection of the ice-making complete water level (e.g., when the ice-making water does not decrease or the like due to disabled ice making) occurs in one ice making unit 41, the control means 48 can quickly detect the abnormality. Note that the first abnormality occurring time is set according to the ice making performance, the site environment and so forth of the down flow type ice making machine 40, and the set values can be freely changed through a control panel (not shown). According to the embodiment, the first abnormality occurring time is set to 5 minutes.

In addition, the control means 48 is set so as to decide that abnormalities have occurred in both ice making units 41, 41 at the same timing when the time from the initiation of the ice making operation to the reception of the detection signal from the last float switch 26 (ice-making completion time) lies within a preset second abnormality occurring time. The ice-making completion time is measured by the second timer 52. Specifically, the second timer 52 operates during the period from the initiation of the ice making operation to the last reception of the detection signal of the ice-making complete water level by the control means 48 to measure the ice-making completion time. Note that the second abnormality occurring time, like the first abnormality occurring time, is adequately set according to the type of the ice making machine, and the set values can be freely changed through the control panel. According to the embodiment, the second abnormality occurring time is set to 15 minutes.

(Operation of Embodiment)

Next, the operation of the down flow type ice making machine 40 according to the embodiment will be described referring to a flowchart in FIG. 2. First, a description will be given of the normal case. At the time of the ice making operation, the circulation pumps 30, 30 of both ice making units 41, 41 are actuated to feed the ice-making waters in the ice-making water tanks 24, 24 to the ice-making surfaces of the individual ice making parts 14 via the ice-making water supply pipes 28, 28 and the ice-making water spray pipes 32, 32. A refrigerant is supplied to each evaporation tube 18 from the freezing system to cool down the ice making part 14. At this time, the control means 48 actuates the second timer 52 to start measuring the ice-making completion time upon initiation of the ice making operation (step S1). The ice-making water supplied to each ice making part 14 exchanges heat with the ice-making surface while flowing down on the ice-making surface, and starts being iced on the ice-making surface. As the ice-making water is iced on the ice-making surface, the ice-making water in the ice-making water tank 24 decreases, causing the float of each float switch 26 to move downward.

When the ice-making water in the ice-making water tank 24 of one ice making unit 41 (e.g., the left one in FIG. 1) reaches the ice-making complete water level first, the associated float switch 26 detects the event, and the control means 48 receives the detection signal from the float switch 26 (detection of the first ice-making complete water level; Yes in step S2). Then, the control means 48 actuates the first timer 50 (step S3) to measure the ice making time difference.

Next, the control means 48 determines whether the time measured by the first timer 50 has passed the first abnormality occurring time or not (step S4). When the time measured by the first timer 50 has not passed the first abnormality occurring time (No in step S4), the control means 48 determines whether the other ice making unit 41 has completed making ice (last ice-making complete water level) or not (step S5). In case of the normal ice operation, the timings at which the ice making processes of both ice making units 41, 41 do not deviate from each other so much and the ice making time difference is small (e.g., one minute or so), ice making of the other ice making unit 41 is completed (Yes in step S5) before the time measured by the first timer 50 passes the first abnormality occurring time (No in step S4). That is, in case of the normal operation, the last ice-making complete water level is detected within the first abnormality occurring time.

Then, the control means 48 stops the first timer 50 (OFF) (step S6), and determines whether the time measured by the second timer 52 lies within the second abnormality occurring time or not (step S7). Because the ice-making completion time is greater than the second abnormality occurring time (No in step S7) in the normal operation, the control means 48 makes the normal decision and stops the second timer 52 (step S8). Then, the control means 48 terminates the ice making operation and moves to the deicing operation (step S9, step S10). Because the excessive water remaining in the ice-making water tank 24 when the ice making operation ice making operation is terminated has a condense impurity, the control means 48 discharges the excessive water before going to the deicing operation. Specifically, the control means 48 reversely rotates the circulation pump 30 of each ice making unit 41 to forcibly release the discharge valve 46 to discharge the excessive water outside.

When the operation is shifted to the deicing operation, the hot gas is fed to the evaporation tubes 18, 18 of both ice making units 41, 41, and deicing water of normal temperature is fed to the back of the ice making plate 16 from an unillustrated deicing water spray pipe. Consequently, the ice making part 14 is heated by the hot gas and the deicing water, deicing the ice blocks formed on and iced with the ice-making surface, so that the ice blocks slide down on the ice-making surface. The ice blocks dropped from the ice making part 14 are received and guided into the ice storage room 34 by the ice guide plate 20. At this time, the ice blocks are deposited to form two heaps in the ice storage room 34 (see FIG. 1). Thereafter, the ice making operation and the deicing operation are repeated in a similar manner to carry out automatic ice making. When the ice storage room 34 becomes full of ice blocks, the ice storage detection means 36 detects ice blocks at the overlapping portion of the two heaps, and the control means 48 decides that the ice storage room 34 is full of ice blocks. Then, the control means 48 performs control to stop the ice making operation until the ice storage detection means 36 does not detect ice blocks. The provision of the ice storage detection means 36 at the center position of both ice making units 41, 41 eliminates the need to provide the ice storage detection means 36 for each ice making unit 41, thus lowering the product cost.

(Occurrence of Abnormality which Delays Ice Making Time)

Suppose that improper opening/closing of the expansion valve 42 or adhesion of a stain to the ice making plate 16 makes it difficult to produce ice blocks on the ice making plate 16 or totally disables production of ice blocks. Then, ice blocks to be produced on the other ice making plate 16 becomes larger, delaying the ice making time in the ice making unit 41 where an abnormality has occurred. Because the ice making operation in the normal ice making unit 41 progresses normally, reduction in the ice-making water in the ice-making water tank 24 in the normal ice making unit 41 is not delayed as done in the ice making unit 41 where an abnormality has occurred. In this case, the control means 48 receives the detection signal on the first ice-making complete water level from the float switch 26 of the normal ice making unit 41 (Yes in step S2). Then, the control means 48 actuates the first timer 50 (step S3) to start measuring the ice making time difference.

Because the ice making time is delayed in the ice making unit 41 where an abnormality has occurred, as mentioned earlier, ice making has not been completed in this ice making unit 41 even when the first abnormality occurring time has elapsed. Therefore, the time measured by the first timer 50 passes the first abnormality occurring time without receiving the signal indicating the completion of ice making from the other ice making unit 41 (Yes in step S4). Consequently, the control means 48 decides that an abnormality has occurred in some ice making unit 41, and stops the first timer 50 (step S11). Then, the control means 48 terminates the ice making operation (step S12), and then carries out abnormality-oriented termination of the operation of the down flow type ice making machine 40 after executing the deicing operation (step S13, step S14).

Because the abnormality detecting method according to the embodiment makes a decision on an abnormality based on the time elapsed from the detection of the first ice-making complete water level as apparent from the above, an abnormality can be detected at an early stage before ice blocks become large. This facilitates the recovery work for the down flow type ice making machine 40, and prevents the ice making plate 16 from being deformed or damaged. Further, a decision on an abnormality is evenly made when the measured time passes the first abnormality occurring time, it is unnecessary to wait for a detection signal on the other ice-making complete water level and is possible to detect an abnormality quickly. Note that the factor to delay the ice making time is not limited to the one explained in the foregoing case. For example, an abnormality to delay the ice making time may occur even when the output of one circulation pump 30 drops due to a failure thereof, thereby reducing the amount of the ice-making water supplied to the ice making part 14. In addition, the ice making time may be delayed even when the ice-making water supply pipe 28 or the ice-making water spray pipe 32 in any ice making unit 41 is clogged with a foreign matter, and the ice making water is not supplied to part or all of the ice making plate 16.

(Occurrence of Abnormality which Shortens Ice Making Time)

For example, multiple ice making may form connected ice, and, what is more, the connected ice may drop from the ice making part 14 and be caught with the ice guide plate 20 in the deicing operation. Then, unfrozen water in the ice making operation may flow along the connected ice caught with the ice guide plate 20 to be discharged into the ice storage room 34 or the like, and may not be collected in the ice-making water tank 24. As a result, the ice-making water in the ice-making water tank 24 decreases quickly, and the float switch 26 of the ice making unit 41 where an abnormality has occurred detects the ice-making complete water level at an earlier timing than that in the normal case. In this case, the control means 48 receives the detection signal from the float switch 26 of the ice making unit 41 where an abnormality (connected ice) has occurred (Yes in step S2), and actuates the first timer 50 (step S3).

Because the ice making operation progresses as normal in the normal ice making unit 41, the ice making time difference between both ice making units 41, 41 is large, so that the abnormal ice making unit 41 cannot receive a detection signal on the ice-making complete water level from the normal ice making unit 41 within the first abnormality occurring time after the detection of the first ice-making complete water level. That is, the time measured by the first timer 50 passes the first abnormality occurring time before the abnormal ice making unit 41 receives the detection signal on the ice-making complete water level from the normal ice making unit 41 (Yes in step S4), the control means 48 decides that an abnormality has occurred in some ice making unit 41 (step S11), and terminates the ice making operation (step S12). Then, the control means 48 stops the operation of the down flow type ice making machine 40 after executing the deicing operation (step S13, step S14). Apparently, even when an abnormality to shorten the ice making time occurs, the abnormality detecting method according to the embodiment can detect the abnormality at an early stage.

The factor to shorten the ice making time is not limited to what has been mentioned in the foregoing case. For example, a foreign matter may enter the discharge valve 46 of the discharge pipe 44 provided at some ice-making water tank 24, causing the discharge valve 46 to be always open. In this case, the ice-making water in the ice-making water tank 24 is naturally discharged via the discharge pipe 44, so that the float switch 26 in this ice-making water tank 24 detects the ice-making complete water level at a very early stage. In another case where the ice storage detection means 36 provided at the ice storage room 34 fails, the ice making operation/deicing operation continues even if the ice storage room 34 is full of ice blocks. Then, the ice blocks overflows to the ice guide plate 20, thereby preventing unfrozen water from being collected into the ice-making water tank 24 in the ice making operation. In the ice making unit 41 where an abnormality has occurred, therefore, the ice-making water decreases faster, so that the float switch 26 detects the ice-making complete water level at a very early timing.

(Occurrence of Abnormalities in Both Ice Making Units in Same Period)

If abnormalities to shorten the ice making time simultaneously occur in both ice making units 41, 41, the ice making time difference between the ice making units 41, 41 is small, so that the last detection of the ice-making complete water level is done (Yes in step S5) before the time measured by the first timer 50 passes the first abnormality occurring time (No in step S4). Accordingly, the control means 48 does not decide the occurrence of an abnormality in step S4. In this case, however, the control means 48 can detect an abnormality based on the time measured by the second timer 52 (ice-making completion time). That is, the control means 48 determines whether the ice-making completion time lies within the second abnormality occurring time or not (step S7), and decides that abnormalities have occurred simultaneously in both ice making units 41.41 (step S15) when the ice-making completion time is less than the second abnormality occurring time (Yes in step S7). Then, the control means 48 terminates the ice making operation (step S16), and stops the operation of the down flow type ice making machine 40 after executing the deicing operation (step S17, step S18). Even if abnormalities to shorten the ice making time simultaneously occur in both ice making units 41, 41, therefore, the abnormality detecting method according to the embodiment can surely detect the abnormalities based on the time measured by the second timer 52.

(Modifications)

Although the embodiment has been illustrated to have two ice making units 41, the abnormality detecting method according to the invention can be implemented even in an ice making machine having one ice making unit 41 or three or more ice making units 41. The abnormality detecting method in case of using three ice making units 41 will be briefly described referring to FIG. 3. At the same time as the ice making operation starts, the second timer 52 is actuated (step S1) to measure the ice-making completion time. Next, when the detection of the first ice-making complete water level is carried out in some ice making unit 41 (Yes in step S2), the control means 48 actuates the first timer 50 (step S3). Thereafter, the control means 48 determines whether the time measured by the first timer 50 passes the first abnormality occurring time or not (step S4). When there is not any abnormality, the detection of the (second) ice-making complete water level is carried out in another ice making unit 41 within the first abnormality occurring time (No in step S4, Yes in step S5).

Then, the control means 48 determines again whether the time measured by the first timer 50 passes the first abnormality occurring time or not (step S6). If an abnormality to delay the ice making time has occurred in the remaining ice making unit 41, the last (third) ice-making complete water level will not be detected within the first abnormality occurring time (Yes in step S6), the control means 48 decides the occurrence of an abnormality, and then terminates the ice making operation (step S8, step S9). Then, the control means 48 executes abnormality-originated termination of the ice making machine after executing the deicing operation (step S10, step S11).

When an abnormality to delay the ice making time has occurred in each of the ice making units 41, 41 except for the ice making unit 41 where the ice-making complete water level has been detected first, the time measured by the first timer 50 will pass the first abnormality occurring time before the second ice-making complete water level is detected (Yes in step S4). That is, because the first abnormality occurring time passes before the ice-making complete water level is detected in the ice making units 41, 41 except for the first ice making unit 41, the control means 48 decides the occurrence of an abnormality (see steps S12 to S15). When every one of the ice making units 41, 41, 41 is normal (Yes in step S7), the first timer 50 is stopped (step S16), and then it is determined whether or not the time measured by the second timer 52 (ice-making completion time) lies within the second abnormality occurring time (step S17), as per the embodiment. In the normal case (No. in step S17), the control means 48 decides the operation as normal (steps S18 to S20). When abnormalities simultaneously occur in the three ice making units 41, 41, 41, the time measured by the second timer 52 lies within the second abnormality occurring time (Yes in step S17), so that the control means 48 decides the occurrence of abnormalities (steps S21 to S24).

As apparent from the above, a decision on an abnormality is made based on the time passed since the first detection of the completion of the ice making operation even when there are three ice making units 41, so that the abnormality can be detected at an early stage. When an abnormality to shorten the ice making time occurs, the abnormality is detected in similar procedures.

Although the float switch 26 is used as detection means in the embodiment, another means, such as a water level sensor, which can detect the ice-making complete water level may be employed adequately. Although the foregoing description of the embodiment has been given of the example in which the down flow type ice making machine 40 where ice-making water flows down at each ice making part 14, the abnormality detecting method according to the invention may be adapted to other automatic ice making machines, such as a spray type ice making machine having a plurality of ice making units. Further, although a decision on an abnormality is carried out using the first timer 50 and the second timer 52 in the embodiment, the ice making time difference and the ice making time may be measured using a single timer.

In addition, the abnormality detecting method according to the embodiment may be combined with the above-described abnormality detecting method according to the related art to detect an abnormality. Specifically, even when the time when every float switch 26 detects the ice-making complete water level (ice-making completion time) exceeds a preset abnormality occurring time, the control means 48 may make a decision on an abnormality. Accordingly, even when abnormalities to delay the ice making time simultaneously occur in all the ice making units 41, the abnormalities can be detected. Furthermore, a method of allowing the control means 48 to make a decision on an abnormality may be added when the time till the detection of the first ice-making complete water level after the start of the ice making operation lies within a predetermined time. 

1. An abnormality detecting method for an automatic ice making machine comprising a plurality of ice making units each having an ice making part to be cooled by a refrigerant supplied from a freezing system, an ice-making water tank that stores ice-making water, a circulation pump that feeds the ice-making water stored in the ice-making water tank to the ice making part, and detection means provided at the ice-making water tank to detect an amount of the ice-making water in the ice-making water tank, and configured to collect unfrozen water which has been fed to the ice making part but has not been frozen into the ice-making water tank, and control means deciding that ice making is completed when every detection means detects that the ice-making water in the ice-making water tank has reached an ice-making complete water level at a time of an ice making operation, wherein upon elapse of a preset first abnormality occurring time from a time of first detection of the ice-making complete water level by the detection means in any one of the ice making units, when the detection means in any one of the other ice making units has not detected the ice-making complete water level, the control means decides that an abnormality has occurred.
 2. The abnormality detecting method according to claim 1, wherein when the detection means in every ice making unit has detected the ice-making complete water level until occurrence of a preset second abnormality occurring time from initiation of the ice making operation, the control means decides that an abnormality has occurred. 